Move Zeroes 539

Question

Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements.

Notice

You must do this in-place without making a copy of the array.

Minimize the total number of operations.

Example

Given nums = [0, 1, 0, 3, 12], after calling your function, nums should be [1, 3, 12, 0, 0].

Solution

双指针法two pointers。第一个指针遇到0就停下（在0之前的位置），第二个指针继续寻找之后第一个非0的元素，找到之后和第一个指针后面的0交换，第一个指针移动一位。即第一个指针和第二个指针之间的元素为0。

代码如下：

public class Solution {
    /**
     * @param nums an integer array
     * @return nothing, do this in-place
     */
    public void moveZeroes(int[] nums) {
        // Write your code here
        if(nums == null || nums.length == 0){
            return;
        }

        int i = -1;;
        for(int j = 0; j < nums.length; j++){
            if(nums[j] != 0){
                i++;
                int temp = nums[i];
                nums[i] = nums[j];
                nums[j] = temp;
            }
        }
    }
}